// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_FILTERS_AUDIO_TIMESTAMP_VALIDATOR_H_
#define MEDIA_FILTERS_AUDIO_TIMESTAMP_VALIDATOR_H_

#include "base/memory/ref_counted.h"
#include "base/time/time.h"
#include "media/base/audio_buffer.h"
#include "media/base/audio_decoder_config.h"
#include "media/base/audio_timestamp_helper.h"
#include "media/base/decoder_buffer.h"
#include "media/base/media_log.h"
#include "media/base/timestamp_constants.h"

namespace media {

class MEDIA_EXPORT AudioTimestampValidator {
public:
    AudioTimestampValidator(const AudioDecoderConfig& decoder_config,
        const scoped_refptr<MediaLog>& media_log);
    ~AudioTimestampValidator();

    // These methods monitor DecoderBuffer timestamps for gaps for the purpose of
    // warning developers when gaps may cause AV sync drift. A DecoderBuffer's
    // timestamp should roughly equal the timestamp of the previous buffer offset
    // by the previous buffer's duration.
    void CheckForTimestampGap(const scoped_refptr<DecoderBuffer>& buffer);
    void RecordOutputDuration(const scoped_refptr<AudioBuffer>& buffer);

private:
    bool has_codec_delay_;
    scoped_refptr<MediaLog> media_log_;

    // Accumulates time from decoded audio frames. We adjust the base timestamp as
    // needed for the first few buffers (stabilization period) of decoded output
    // to account for pre-skip and codec delay. See CheckForTimestampGap().
    std::unique_ptr<AudioTimestampHelper> audio_output_ts_helper_;

    base::TimeDelta audio_base_ts_;

    // Initially false, set to true when we observe gap between encoded timestamps
    // match gap between output decoder buffers.
    bool reached_stable_state_;

    // Counts attempts to adjust |audio_output_ts_helper_| base offset in effort
    // to form expectation for encoded timestamps based on decoded output. Give up
    // making adjustments when count exceeds |limit_unstable_audio_tries_|.
    int num_unstable_audio_tries_;

    // Limits the number of attempts to stabilize audio timestamp expectations.
    int limit_unstable_audio_tries_;

    // How many milliseconds can DecoderBuffer timestamps differ from expectations
    // before we MEDIA_LOG warn developers. Threshold initially set from
    // kGapWarningThresholdMsec. Once hit, the threshold is increased by
    // the detected gap amount. This avoids log spam while still emitting
    // logs if things get worse. See CheckTimestampForGap().
    uint32_t drift_warning_threshold_msec_;

    DISALLOW_COPY_AND_ASSIGN(AudioTimestampValidator);
};

} // namespace media

#endif // MEDIA_FILTERS_AUDIO_TIMESTAMP_VALIDATOR_H_